Apparatus for molding a hollow molded article

ABSTRACT

First and second semi-finished molded articles and a third semi-finished molded article are molded simultaneously so as to have joint end faces by using a slide die, a fixed die, and first and second slide cores fitted to the fixed die. The slide die with the third semi-finished molded article remaining thereon is moved toward the first and second slide cores, and their respective joint end faces are registered. Heating surfaces are inserted between the joint end faces. After melting the joint end faces, the heating surfaces are retracted, and the molding device is closed to weld the joint end faces.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No. 11/117,529filed Apr. 29, 2005, now U.S. Pat. No. 7,575,704, which claims priorityto Japanese Application No. 2004-135056 filed Apr. 30, 2004; theabove-noted applications incorporated herein by reference in theirentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of molding a hollow moldedarticle in which, in primary molding, semi-finished molded articleswhich make a pair are molded simultaneously so as to have joint faces byusing a fixed die and a movable die capable of closing a molding deviceand, in secondary molding, the movable die with one semi-finished moldedarticle remaining thereon is moved with respect to the fixed die tothereby cause the one semi-finished molded article to be superposed onthe other semi-finished molded article so that their respective jointfaces are opposed to each other, and the superposed joint faces arewelded by closing the movable die with respect to the fixed die or bypressing the semi-finished molded articles in a molding device, therebyobtaining a hollow molded article from the semi-finished moldedarticles, as well as the hollow molded article, and an apparatus formanufacturing the same.

2. Description of the Related Art

A molding method using an injection molding machine is known as onemethod of manufacturing a synthetic resin-made hollow molded articlewhich is obtained by complex joining, including a bent pipe, an intakemanifold, a tank, and the like. This injection molding machine consistsof a set of molding devices, as also shown in JP-A-62-87315 andJP-A-6-246781. A male die and a female die for forming one hollow moldedarticle are provided in one molding device of the set of moldingdevices, while a female die and a male die for forming the other hollowmolded article are provided in the other molding device. Accordingly,if, by using these molding devices, hollow products are formed as twosplit semi-finished hollow articles or split articles in primarymolding, and their split surfaces are abutted against each other and amolten resin is injected and filled into the abutted joint space insecondary molding, the pair of semi-finished hollow articles areproduced as one hollow product in which they are joined at the splitsurfaces. As a result, the hollow molded article can be manufactured byinjection molding. According of this molding method using the injectionmolding machine, there are advantages in that it is possible tofabricate a hollow product which is completely sealed and fabricate ahollow product with a uniform thickness, and that it is possible to copewith complex shapes. However, since a molten resin for joining must beinjected in secondary molding, the structure of the injecting machinebecomes long or a long molding time is required, or the structure of themolding device becomes complex. Furthermore, if the secondary injectionpressure is small, the joining force is weak, whereas if it is large tothe contrary, there is a possibility of the molten resin leaking fromthe joint space to the interior of the hollow product.

Further, JP-A-6-305028 discloses a manufacturing method in which atubular first member made of a thermoplastic resin and a similar tubularsecond member made of a thermoplastic resin are opposed to each other,an electrically conductive member is clamped by the opposing end faces,and the end faces are welded by subjecting the electrically conductivemember to induction heating, thereby manufacturing a tubular article. Inaddition, the following method of manufacturing a hollow product isshown in JP-A-7-16945. Namely, in primary molding, first and secondsemi-finished hollow articles are molded simultaneously by using a slidedie and a movable die so as to have joint portions. Then, in secondarymolding, the slide die is slid upwardly with respect to the movable die,and one of the first and second semi-finished hollow articles molded inthe primary molding is superposed on the other semi-finished hollowarticle such that their joint portions are opposed to each other. Theinner surface sides of the joint portions of the superposed first andsecond semi-finished hollow articles are heated by a heater, or areheated by hot air so as to melt partially. Then, the joint portions arepressed and welded by a pressing member, thereby obtaining a hollowproduct from the first and second semi-finished hollow articles.

According to the invention disclosed in JP-A-6-305028, since it isunnecessary to inject a molding resin for joining when the end faces ofthe first and second members are joined, there is an advantage in thatthe injecting machine or the injection operation becomes simple.However, since foreign objects are embedded in the joint faces, thereare also problems. For example, since the embedded electricallyconductive member is made of a metal, there are cases where it exhibitsa shielding effect with respect to radio waves, and cases where itgenerates heat, so that applications are sometimes limited. Furthermore,since the metallic electrically conductive member is interposed orembedded at the joint faces, i.e., since the joining is not that betweensynthetic resins, but that of different materials, i.e., a metal and asynthetic resin, the joining force can possibly be weak. In addition,although the JP-A-6-305028 does not especially show an apparatus usedfor carrying out the respective methods of molding the first and secondmembers or for carrying out the method of joining the first and secondmembers, it is supposed that the first and second members after beingremoved from the molding device are joined by using a special apparatus.Hence, these first and second members are likely to be affected bydisturbances, and there are cases where their temperatures, shapes, andthe like undergo change over time, possibly resulting in a decline inthe precision of the molded product. In addition, it is estimated thatthe manufacturing process is made complex.

According to the invention described in JP-A-7-16945, since the innersides of the joint portions are heated and welded in a state in thefirst and second semi-finished hollow articles are placed in the moldingdevice, advantages are obtained in that the outer sides of the jointportions are not melted and deformed, and that only portions necessaryfor joining are melted, so that energy for melting can be small.Furthermore, since the secondary molding for joining the pair ofsemi-finished hollow articles is carried out by using the same moldingdevice used in the primary molding for molding the pair of semi-finishedhollow articles, there are advantages in that the apparatus formanufacturing a high-precision hollow product is inexpensive and thatthe hollow product can be manufactured at low cost. However, since theheater is embedded, the above-described problems are encountered. Inaddition, since the heater is in the form of wires, there is noguarantee that the end faces which are joined are uniformly melted. Onthe other hand, according to the method of joining by melting by hotair, since the hot air is large in compressibility and has a small heatcapacity, it is estimated that it is technically difficult to supply hotair uniformly over the entire areas of the joint portions and touniformly melt them. In addition, since the molten joint portions areadapted to be pressed and welded by a pressing member which isespecially prepared, a higher cost of the manufacturing apparatus canresult.

SUMMARY OF THE INVENTION

The present invention has been devised in view of the above-describedproblems, and specifically its object is to provide a method of moldinga hollow molded article in which the strength of the joint portions ofthe semi-finished hollow articles is sufficiently large, which is freeof the problem of injection that the molding process becomes complexduring secondary molding, the problem of selection of resin, and thelike, and which does not especially require a pressing member forpressing and contact bonding the joint portions, as well as an apparatusfor manufacturing the same. Another object of the invention is toprovide an inexpensive hollow molded product which has large bondingstrength despite the fact that a plurality of semi-finished moldedarticles are joined.

To attain the above object, the manufacturing process in accordance withthe invention consists of primary molding and secondary molding. In theprimary molding, semi-finished molded articles which make a pair or aplurality of semi-finished molded articles are molded simultaneously soas to have joint faces. The joint faces are then melted and contactbonded in the secondary molding. During this secondary molding, aheating module having heating surfaces, preferably a heating modulehaving heating surfaces similar to the joint faces, is inserted betweenthe joint faces, and the joint faces are melted uniformly. Then, afterthe heating module is retracted, the joint faces are contact bonded. Thecontact bonding is arranged to be performed by a clamping apparatus usedin the primary molding. Thus, to attain the above objects, in accordancewith a first aspect of the invention, there is provided a method ofmolding a hollow molded article, comprising molding a pair ofsemi-finished molded articles each of which has a joint face to bejointed by using a molding device including a fixed die and a movabledie capable of closing the molding device, moving the movable die inwhich one of the semi-finished molded articles remain with respect tothe fixed die so that the respective faces of the semi-finished moldedarticles are opposed to each other, inserting a heating module havingheating surfaces between the joint faces of the semi-finished moldedarticles, causing the heating module to melt the joint faces andretracting the heating module, and press bonding the joint faces byclosing the molding device or pressing the semi-finished molded articlesinside the molding device.

In accordance with a second aspect of the invention, there is provided amethod of molding a hollow molded article, comprising molding first tothird semi-finished molded articles each of which has a joint face to bejointed by using a molding device including a fixed die, a movable diecapable of closing the molding device, and a pair of slide cores fittedto the fixed die, moving the movable die in which the thirdsemi-finished molded article remains is moved with respect to the slidecores on the fixed die so that the respective faces of the semi-finishedmolded articles are opposed to one another, spacing apart the jointfaces of the first to third semi-finished molded articles, inserting aheating module having heating surfaces between the joint faces, causingthe heating module to melt the joint faces and retracting the heatingmodule, and press bonding the joint faces by closing the molding deviceor pressing the semi-finished molded articles inside the molding device.

In accordance with a third aspect of the invention, in the moldingmethod according to the first or second aspect, the heating surfacessimilar to the joint faces are inserted between the joint faces in anon-contact manner to melt the joint faces. In accordance with a fourthaspect of the invention, there is provided a hollow molded articlecomprising a plurality of semi-finished molded articles which are moldedto have joint faces in primary molding, and a heating module having aheating surface, wherein the joint faces are melted and contact bondedat the joint faces by the closing of a same molding device as that usedin the primary molding or by pressing the semi-finished molded articlesinside the molding device, and wherein the joint faces are melted andcontact bonded after the heating module heats and melts the joint facesand is retracted.

In accordance with a fifth aspect of the invention, there is provided anapparatus for molding a hollow molded article, comprising a combinationof a molding device and a heating module, the molding device including afixed die, a movable die, and a first and a second slide core fitted tothe fixed die, wherein if the movable die is clamped to the fixed die ata first position, a first and a second cavity for simultaneously moldinga first and a second semi-finished molded article having joint faces areformed by the first and the second slide core and the movable die, and athird cavity for simultaneously molding a third semi-finished moldedarticle similarly having joint faces is formed by the fixed die and themovable die, wherein if the movable die is moved by a predeterminedamount toward the first and the second slide core, the first to thirdcavities are registered with each other, and at a registered secondposition surfaces making up the first to third cavities are adapted tobe spaced apart so as to secure a space of a predetermined size and toeffect molding device clamping, and wherein the heating module hasheating surfaces similar to the joint faces of the first to thirdsemi-finished molded articles and is provided in such a manner as to becapable of being inserted into or retracted from the space formed by thespaced-apart surfaces making up the first to third cavities.

As described above, in accordance with the invention, the arrangementprovided is such that in primary molding, semi-finished molded articleswhich make a pair are molded simultaneously so as to have joint faces byusing a molding device including a fixed die and a movable die capableof closing the molding device and, in secondary molding, the movable diewith one semi-finished molded article remaining thereon is moved withrespect to the fixed die to thereby cause the one semi-finished moldedarticle to be superposed on another semi-finished molded article so thattheir respective joint faces are opposed to each other, so as to obtaina hollow molded article from the semi-finished molded articles whichmake a pair by joining the superposed joint faces. A heating modulehaving heating surfaces is inserted between the joint faces of thesemi-finished molded articles before completion of a molding deviceclosing step, and the then heating module melts the joint faces andretracts. The molding device is closed or the semi-finished moldedarticles are pressed inside the molding device are so as to melt andcontact bond the joint faces. Namely, since the secondary molding iscarried out by using the same molding device without removing thesemi-finished molded articles from the molding device used in theprimary molding, it is unnecessary to transfer the semi-finished moldedarticles to a welding jig. Since the adjustment of the jig by takinginto account a change in the shrinkage over time of the semi-finishedmolded articles is made unnecessary, it is possible to easilymanufacture a hollow molded article excelling in precision. In addition,since the adjustment of the welding jig is not required, anotheradvantage is obtained in that fusion strength becomes uniform. Moreparticularly, according to a related hot plate welding method, themolded article must be inserted in a welding jig after the moldedarticle is removed from the molding device. However, if the moldedarticle is removed from the molding device, the molded article undergoesdeformation, so that the insertion becomes difficult. As a result, thewelding of a molded article whose joint surface is curved becomesdifficult, so that the related hot plate welding method is frequentlyused in the welding of molded articles whose joint surfaces are flat.According to the invention, however, since heating is effected in themolding device used in the primary molding, it is possible to obtain ahollow molded article with high dimensional accuracy without beingaffected by the shape of the joint surfaces.

In particular, according to the invention, the heating module having theheating surfaces is inserted between the joint faces of thesemi-finished molded articles, is caused to melt the joint faces, and isretracted. The molding device is then closed or the semi-finished moldedarticles are pressed inside the molding device to melt and contact bondthe joint faces. Therefore, it is possible to obtain advantages peculiarto the invention in that foreign objects are absent between the jointfaces, the resins are joined, and a hollow molded article whose jointportions have large strength is obtained from semi-finished moldedarticles. At this juncture, since heating is effected in the state inwhich the semi-finished molded articles remain in the molding device,control of the position of the heating module is accurate. In addition,since the joint faces are heated by the heating surfaces, melting andcontact bonding occurs over the overall surfaces of the joint faces.Furthermore, since heating is effected in the state in which thesemi-finished molded articles remain in the molding device, welding canbe allowed to take place before the semi-finished molded articlescompletely solidify. Hence, a hollow molded article can be manufacturedby saving energy.

In addition, the manufacturing method according to the invention is freeof the problem of injection that the molding process becomes complexduring secondary molding, the problem of selection of resin, and thelike, and a pressing member for pressing and contact bonding the jointportions is not especially required. Therefore, the hollow moldedarticle can be manufactured at low cost.

The hollow molded article according to the invention is one in which aplurality of semi-finished molded articles molded to have joint faces inprimary molding are melted and contact bonded at the joint faces by theclosing of the same molding device as that used in the primary moldingor by pressing the semi-finished molded articles inside the moldingdevice. The hollow molded article comprises a heating module havingheating surfaces for heating and melting the joint faces, wherein thejoint faces are melted and contact bonded after the heating module heatsand melts the joint faces and is retracted. Therefore, despite the factthat a plurality of semi-finished molded articles are joined, thebonding strength is large, and precision is high.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1D are diagrams illustrating an embodiment of the invention,in which FIG. 1A is a perspective view illustrating an example of ahollow molded article (curved pipe), FIG. 1B is a cross-sectional viewillustrating an apparatus for manufacturing the hollow molded articlewith a molding device closed in accordance with a first embodiment, andFIGS. 1C and 1D are cross-sectional views taken in the direction ofarrows along line C-C and line D-D, respectively, in FIG. 1B;

FIG. 2 is a cross-sectional view illustrating a state in which thehollow molded article is being manufactured with a heating moduleinserted in accordance with the first embodiment;

FIGS. 3A and 3B are diagrams illustrating other examples of hollowmolded articles in accordance with the embodiments, in which FIG. 3A isa front elevational view illustrating a first other example, and FIG. 3Bis a cross-sectional view illustrating a second other example;

FIGS. 4A and 4B are diagrams illustrating an apparatus for manufacturinga hollow molded article in accordance with a second embodiment, in whichFIG. 4A is a cross-sectional view illustrating a state in which themolding device is closed, and FIG. 4B is a cross-sectional viewillustrating a state in which the hollow molded article is beingmanufactured with the heating module inserted; and

FIG. 5 is a perspective view schematically illustrating an example of anapparatus for driving the heating module.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First, a description will be given of an apparatus for manufacturing acurved pipe C in which first and second semi-finished molded articles A1and A2 which, as seen in a side view, occupy about one-fourth of acircumference and a semicircular arc-shaped third semi-finished moldedarticle B are joined at their joint faces a and b, and a and a, and havea semicircular arc shape as a whole, as shown in FIG. 1A. Amanufacturing apparatus in accordance with a first embodiment formanufacturing or molding the curved pipe C is shown in FIG. 1B in astate in which its molding device is closed. This manufacturingapparatus is roughly comprised of a fixed die 1; a movable die 29 whichis opened or closed with respect to this fixed die 1; a slide die 30provided on the movable die 29 in such a manner as to be capable ofbeing slidingly driven in the vertical direction in FIG. 1B; and a pairof first and second slide cores 11 and 12 which are mounted in a recessof the fixed die 1 in such a manner that their open surfaces are inalignment with a parting line P when the molding device is clamped.Although the apparatus for manufacturing a hollow molded article inaccordance with this embodiment has a heater, which will be describedlater in detail, this heater is not shown in FIG. 1B. It should be notedthat a clamping apparatus for clamping the movable die 29 with respectto the fixed die 1 is not shown, either.

A recess 3 of a predetermined size, which is recessed in the inwarddirection from the parting line P, is formed at a lower position in thefixed die 1 in FIG. 1B. This recess 3 is for molding an inner peripheralsurface of the third semi-finished molded article B. Although thisrecess 3 as a whole is shown as being curved in FIG. 1B, this portion isspecifically constituted by a small convex portion 2, as shown in FIG.1C. Since this convex portion 2 is curved as a whole, this portion isshown as the recess 3 in the cross-sectional view of FIG. 1B. A pair ofvoid spaces 5 of a predetermined size, in which a pair of inclined pins35 are respectively accommodated during primary molding, are formed onboth sides of the recess 3.

The pair of first and second slide cores 11 and 12 are fitted in anupper portion of the fixed die 1 in such a manner as to be movable inthe left and right direction in FIG. 1B, i.e., in the direction towardand away from the parting line P, and in the vertical direction. Thesefirst and second slide cores 11 and 12 as a whole have a substantiallytrapezoidal shape in a side view, and their outwardly-facing sidesurfaces are formed as tapered surfaces 13 which are widened toward theparting line P side. A pair of guide holes 14 which are inclined in theopposite direction to the tapered surface 13 are respectively providedin the first and second slide cores 11 and 12. Accordingly, as will beexplained in the section on the operation, if the slide die 30 is openedwith the inclined pins 35 of the slide die 30 entered in the guide holes14, the interval between the first and second slide cores 11 and 12becomes greater due to the action of the inclined surfaces 13 when thefirst and second slide cores 11 and 12 are drawn out from the fixed die1. A pair of recesses 15 having the shape of a circular arc of aboutone-fourth of a circumference are respectively formed in corner portionsfacing the parting line P side of the first and second slide cores 11and 12 thus constructed. FIG. 1D is a cross-sectional view taken in thedirection of arrows along line D-D in FIG. 1B. As shown in this drawing,these recesses 15 are constituted by small recesses 15′ for moldingouter peripheral surfaces of the first and second semi-finished moldedarticles A1 and A2, and ends of these recesses 15′ are shown as therecesses 15 in FIG. 1B.

Unillustrated gates, which communicate with first and second sprues 16and 17, are respectively open in upper portions of the recesses 15constructed as described above. These first and second sprues 16 and 17communicate with a resin hole of a locating ring 20 of a fixing diemounting plate 1′ through a runner 18 and a main sprue 19 which areformed between the fixed die 1 and the fixed die mounting plate 1′. Inaddition, the runner 18 extends downward as well, and a sprue 21communicating with this runner 18 is open in an apex portion of therecess 3 of the fixed die 1 through an unillustrated gate. The mainsprue 19, the runner 18, and the sprues 16, 17, and 21 are for primarymolding, and runners, sprues, and the like for secondary molding are notprovided in this embodiment. Therefore, the molding device has a simplestructure.

A semicircular arc-shaped core 33, which projects from the parting lineP toward the fixed die 1 and makes a pair with the recess 3 of the fixeddie 1, is provided on the parting line P side of the slide die 30 on thelower side in FIG. 1B. This core 33 is for molding an outer surface ofthe third semi-finished molded article B, and is constituted by a recess32, as shown in FIG. 1C. However, since this recess 32 is curved, it isshown as the core 33 in the cross-sectional view of FIG. 1B. The pair ofinclined pins 35 are attached to this core 33 with a predeterminedinterval provided in the vertical direction in such a manner as toproject toward the respective void spaces 5 in the fixed die 1 and to beinclined away from each other. These inclined pins 35 are provided atthe same angle as that of the guide holes 14 respectively formed in thefirst and second slide cores 11 and 12.

A core 36, which makes a pair with the recesses 15 of the first andsecond slide cores 11 and 12, is provided on an upper portion of theslide die 30 in such a manner as to project from the parting line Ptoward the fixed die 1. A spacer portion 37 is provided integrally on anapex portion of this core 36. The interval between the first and secondslide cores 11 and 12 is widened by this spacer portion 37, and theirtapered surfaces 13 are respectively brought into contact with thetapered surfaces of the fixed die. It should be noted that referencenumeral 38 in FIG. 1B denotes an ejector or an ejector pin for ejectingthe molded article.

According to this embodiment, as shown in FIG. 2, a heating module 40 isalso provided for heating and melting the joint faces a and b of thefirst to third semi-finished molded articles A1, A2, and B. This heatingmodule 40 is comprised of first and second heating surfaces 41 and 42formed by planar heaters constituted by such as sheathed heaters,ceramic heaters, and induction heaters, as well as a heating surfaceholder for holding these heating surfaces 41 and 42. The heating surfaceholder is formed by a bowl portion 46 which is curved in a side view anda spacer portion 47 projecting from an apex portion of this bowl portion46. The first heating surface 41 is fitted to the inner surface of thebowl portion 46, and the second heating surfaces 42 are fitted to theouter peripheral surface thereof. The second heating surfaces 42 haveheating extended surfaces 43 which extend toward the spacer portion 47.According to this embodiment, as for the heating module 40, its heatingsurfaces 41 and 42 have shapes such as those shown in FIG. 2 since themolded article is the curved pipe C. However, the first heating surface41 corresponds to ends of a cavity Cb indicated by reference charactersb′ and b′ in FIG. 1C, while each of the second heating surfaces 42corresponds to ends of a cavity Ca1 indicated by reference characters a′and a′ in FIG. 1D. In addition, the heating extended surfaces 43 areadapted to melt the joint faces a shown in FIG. 1A.

An example of a driving apparatus for inserting the heating module 40thus constructed between the fixed die 1 and the slide die 30 orretracting it from therebetween is shown in FIG. 5. Namely, the drivingapparatus shown in FIG. 5 is comprised of, among others, a pair of guiderails 71 mounted on a side portion of the fixed die 1; a supportingframe 72 which is guided by the guide rails 71; a hydraulicpiston/cylinder unit 70 for driving this supporting frame 72; and ahydraulic power source for supplying or discharging working oil to orfrom the hydraulic piston/cylinder unit 70 through supply and dischargehoses 73. Further, the heating module 40 is mounted on a distal end ofthe supporting frame 72. This heating module 40 is provided with theabove-described heaters, and electric power is adapted to be fed tothese heaters through cables 76 at all times or when the temperature hasdropped to a predetermined level. In addition, a heating moduleinsertion port 77 is provided in side portions of the fixed die 1 andthe slide die 30. Accordingly, when working oil is supplied to ordischarged from the hydraulic piston/cylinder unit 70 in interlockingrelation to the movement of the slide die 30, the heating module 40 isinserted into the gaps between the joint faces a and b, and a and a, oris retracted to the position shown in FIG. 5.

It should be noted that an arrangement may be provided such that theheating module 40 is attached to, for example, an arm of a robot and isinserted into or retracted from the gaps between the fixed die 1 and theslide die 30, i.e., the gaps between the joint faces a and b, and a anda, in interlocking relation to the movement of the slide die 30. Such arobot, however, is not shown in the drawing.

Next, a description will be given of a molding method for manufacturingthe curved pipe C made of a synthetic resin by using the above-describedmanufacturing apparatus. The slide die 30 is slidingly driven to aprimary molding position, i.e., the position shown in FIG. 1B, and isclamped by an unillustrated clamping apparatus. Then, the third cavityCb for molding the third semi-finished molded article B is formed by therecess 3 of the fixed die 1 and the core 33 of the slide die 30. At thesame time, the first cavity Ca1 for molding the first semi-finishedmolded article A1 is formed by the recess 15 of the first slide core 11and the core 36 of the slide die 30, and a second cavity Ca2 for moldingthe second semi-finished molded article A2 is formed by the recess 15 ofthe second slide core 12 and the core 36 of the slide die 30.

A plasticized molten resin is injected from a nozzle of an unillustratedinjection machine into a main sprue 19. The molten resin issubstantially simultaneously filled into the respective cavities Cb,Ca1, and Ca2 through the gates from the runner 18 and the first, second,and third sprues 16, 17, and 21. As a result, the first and secondsemi-finished molded articles A1 and A2 and the third semi-finishedmolded article B are molded substantially simultaneously. Thesemi-finished molded articles are left in the molding device as they areuntil they cool and solidify to some degree. This completes the primarymolding.

Next, the movable die 29, i.e., slide die 30, is opened. When the die isopened, depending on the shapes and areas of the semi-finished moldedarticles A1, A2, and B or the presence or absence of projections, thefirst and second semi-finished molded articles A1 and A2 respectivelyremain in the first and second slide cores 11 and 12, while the thirdsemi-finished molded article B remains on the slide die 30. The slidedie 30 is subsequently slid to a second position on the upper side inFIG. 1B. Then, the joint faces a and b, and a and a, of the first andsecond semi-finished molded articles A1 and A2 and the thirdsemi-finished molded article B are registered. Temporary clamping iseffected. As a result of this temporary clamping, the inclined pins 35enter the guide holes 14 of the first and second slide cores 11 and 12.Then, the slide die 30 is opened by a predetermined amount. As a result,the slide die 30 is opened with a predetermined amount with respect tothe first and second slide cores 11 and 12, i.e., the parting line P. Inaddition, the first and second slide cores 11 and 12 are driven inmutually opening directions by the action of the inclined pins 35, andare opened by a predetermined amount. Namely, the joint faces a and abetween the first and second semi-finished molded articles A1 and A2, aswell as the joint faces a and b between, on the one hand, the first andsecond semi-finished molded articles A1 and A2 and, on the other hand,the third semi-finished molded article B, are spaced apart withpredetermined intervals. At this juncture, working oil is supplied tothe hydraulic piston/cylinder unit 70. Then, the heating module 40 isinserted between the joint faces a and b, and a and a. The joint faces aand b, and a and a, are heated and melted in a non-contact manner.Alternatively, after the heating module 40 is inserted, the intervalsbetween the heating surfaces 41, 42, and 43 and the joint faces a and bare narrowed so as to perform heating and melting effectively.

The state in which the heating module 40 is thus inserted or is heatingis shown in FIG. 2. After the joint faces a and b, and a and a, aremelted, the heating module 40 is drawn out, and the molding device isclamped. As a result of this clamping force, the first and secondsemi-finished molded articles A1 and A2 and the third semi-finishedmolded article B are welded at their joint faces a and b. At the sametime, the first and second slide cores 11 and 12 are driven in mutuallyapproaching directions by the action of the inclined pins 35, so thatthe first and second semi-finished molded articles A1 and A2 are weldedat their joint faces a and a. The slide die 30 is opened after thesemi-finished molded articles are cooled and solidified. Then, thecurved pipe C shown in FIG. 1A projects by means of the ejector 38. Theslide die 30 is slid to the first position shown in FIG. 1B, and primarymolding is carried out, as described above. Thereafter, the curved pipeC is manufactured in the same way.

Next, a description will be given of a second embodiment of theinvention with reference to FIGS. 4A and 4B. Although the curved pipe Cshown in FIG. 1A can also be manufactured according to the secondembodiment, a description will be given of an example of manufacturing acurved pipe C′ having flanges F at its both ends from first and secondsemi-finished molded articles A1′ and A2′ and a third semi-finishedmolded article B′, as shown in FIG. 3A. It should be noted that thoseelements similar to the component elements of the above-described firstembodiment will be denoted by the same reference numerals, or the samereference numerals will be appended with a prime mark (′), and aredundant explanation will be omitted. The manufacturing apparatus inaccordance with the second embodiment has a pair of slide cores 11′ and12′ which are embedded in a fixed die 1′ at a predetermined angle. Thesefirst and second slide cores 11′ and 12′ have first and secondpiston/cylinder units 51 and 52 which operate hydraulically orpneumatically. First and second cores 53 and 54 are adapted to be drivenin the directions of open arrows by these piston/cylinder units 51 and52. A first cavity Ca1′ for molding the first semi-finished moldedarticle A1′ is formed by a distal end portion of the first core 53 and acore 36′ of a slide die 30′, and a second cavity Ca2′ for molding thesecond semi-finished molded article A2′ is formed by a distal endportion of the second core 54 and the core 36′ of the slide die 30′. Apair of recesses 55 for molding the pair of flanges F are formed inperipheries of a core 33′ of the slide die 30′.

According to this embodiment, the gates are so-called tab gates whichare open to the first to third cavities Ca1′, Ca2′, and Cb′ through tabsprovided on the end faces of these cavities Ca1′, Ca2′, and Cb′, runners16′, 17′, and 21′ do not appear in FIG. 4A. In addition, as for aheating module 40′, the heating module 40′ itself makes up heatingsurfaces.

According to the second embodiment as well, molding can be performed ina manner similar to that of the above-described embodiment, so that adetailed description will not be given. The slide die 30′ is slid to thefirst position for primary molding shown in FIG. 4A. Working oil issupplied to the first and second piston/cylinder units 51 and 52 todrive the first and second cores 53 and 54 to the position shown in FIG.4A, and clamping is carried out. Then, the third cavity Cb′ for moldingthe third semi-finished molded article B′ is formed by the recess 3 ofthe fixed die 1′ and the core 33′ of the slide die 30′. At the sametime, the first cavity Ca1′ for molding the first semi-finished moldedarticle A1′ is formed by a recess 15′ of the first core 53 and the core36′ of the slide die 30′, and the second cavity Ca2′ for molding thesecond semi-finished molded article A2′ is formed by the recess 15′ ofthe second core 14 and the core 36′ of the slide die 30′.

A plasticized molten resin is injected from a nozzle of an unillustratedinjection machine into the respective cavities Cb′, Ca1′, and Ca2. As aresult, the first and second semi-finished molded articles A1′ and A2′and the third semi-finished molded article B′ are molded substantiallysimultaneously. The semi-finished molded articles are left in themolding device as they are until they cool and solidify to some degree.This completes the primary molding.

Next, the slide die 30′ is opened. When the die is opened, the first andsecond semi-finished molded articles A1′ and A2′ respectively remain inthe first and second cores 53 and 54, while the third semi-finishedmolded article B′ remains on the slide die 30′. The slide die 30′ issubsequently slid to the second position on the upper side in FIG. 4A.Then, the joint faces a and b, and a and a, of the first and secondsemi-finished molded articles A1′ and A2′ and the third semi-finishedmolded article B′ are registered, as described above. The first andsecond cores 53 and 54 are retracted, as shown in FIG. 4B. The fixed die1′ and the slide die 30′ are spaced apart from each other, and the firstand second cores 53 and 54 have been retracted. Therefore, the jointfaces a and a between the first and second semi-finished molded articlesA1′ and A2′, as well as the joint faces a and b between, on the onehand, the first and second semi-finished molded articles A1′ and A2′and, on the other hand, the third semi-finished molded article B′, arespaced apart with predetermined intervals. Accordingly, the heatingmodule 40′ is inserted between these joint faces a and b, and a and a,by the hydraulic piston/cylinder unit 70 to heat and melt these jointfaces a and b, and a and a, as described above.

The state in which the heating module 40′ is thus inserted or is heatingis shown in FIG. 4B. After the joint faces a and b, and a and a, aremelted, the heating module 40′ is drawn out, and the molding device isclamped. In addition, working oil is supplied to the first and secondpiston/cylinder units 51 and 52 to drive the first and second cores 53and 54 in the directions shown in FIG. 4A. As a result of this clampingforce, the first and second semi-finished molded articles A1′ and A2′and the third semi-finished molded article B′ are welded at their jointfaces a and b. Also, as the first and second cores 53 and 54, which areinclined inwardly with respect to each other, are driven, the first andsecond semi-finished molded articles A1′ and A2′ are welded at theirjoint faces a and a. The slide die 30′ is opened after the semi-finishedmolded articles are cooled and solidified. Then, the curved pipe C′ withthe flanges F shown in FIG. 3A projects by means of an ejector 38′. Theslide die 30′ is slid to the first position shown in FIG. 4A, andprimary molding is carried out, as described above. Thereafter, thecurved pipe C′ is manufactured in the same way.

Although in the above-described embodiments a description has been givenof examples in which the curved pipes C and C′ are manufactured, it isclear that it is possible to similarly manufacture a curved pipe-likehollow article in which ends of the curved pipe C or C′ are closed. Itis also clear that it is possible to manufacture a spherical hollowarticle C″ from three semi-finished molded articles A1″, A2″, and B″, asshown in FIG. 3B. Accordingly, molded articles in which a portion isopen as in the curved pipes C and C′ are also included among the hollowmolded articles. In addition, it is also clear that the invention can beimplemented by a rotating die instead of the slide die.

1. An apparatus for molding a hollow molded article, comprising: acombination of a molding device and a heating module, the molding deviceincluding a fixed die, a movable die, and a first and a second slidecore fitted to the fixed die, wherein when the movable die is clamped tothe fixed die at a first position, a first and a second cavity forsimultaneously molding a first and a second semi-finished molded articlehaving joint faces are formed by the first and the second slide core andthe movable die, and a third cavity for simultaneously molding a thirdsemi-finished molded article similarly having joint faces is formed bythe fixed die and the movable die; wherein when the movable die is movedby a predetermined amount toward the first and the second slide core,the first to third cavities are registered with each other, and at aregistered second position surfaces making up the first to thirdcavities are adapted to be spaced apart so as to secure a space of apredetermined size and to effect molding device clamping; and whereinthe heating module has heating surfaces similar to the joint faces ofthe first to third semi-finished molded articles and is provided in sucha manner as to be capable of being inserted into or retracted from thespace formed by the spaced-apart surfaces making up the first to thirdcavities.
 2. The apparatus for molding a hollow molded article of claim1, wherein at least one of the first, second, and third cavities iscurved.